Single Amino Acid Change Allows Bat Coronavirus to Infect Humans

A single amino acid change can transform a bat-only coronavirus into a virus capable of infecting humans, according to researchers from UC San Francisco, the Pasteur Institute, and the Fred Hutchinson Cancer Center. The study, published in Cell Host & Microbe, explains how benign animal viruses adapt to cause serious human diseases.

How does a single amino acid change infection?

The research team identified a viral protein called OrfB9 as the primary driver of this transition. While the OrfB9 protein contains roughly 100 amino acids, the coronavirus and a similar bat-only virus, RaTG13, differ by only one.

This minute difference alters how the virus interacts with the host. In human cells, the coronavirus version of OrfB9 disables the immune system’s alarm mechanism. This failure allows the virus to replicate and spread through the human body.

In contrast, the RaTG13 version behaves differently in bat cells. According to the study, it activates an immune protein that helps the bat’s body suppress the virus, keeping the infection in check.

Did You Know? The researchers conducted these experiments using the first-ever lab-cultured lung cell line derived from the greater horseshoe bat.

Why is the OrfB9 protein significant?

The ability of a virus to bypass immune defenses is what enables zoonotic spillover. By comparing how coronavirus and RaTG13 interact with immune proteins in both bat and human lung cells, researchers can see the exact point of failure in human immunity.

Nevan J. Krogan, the study’s lead author, stated that remarkably small genetic changes can be the difference between a virus that stays in bats and one that jumps to humans to cause catastrophic disease.

Expert Insight: Samantha Carter notes that the discovery of a single-point mutation driving host-switching underscores the volatility of viral evolution. The stakes are high because it suggests that highly dangerous pathogens may emerge from nearly identical, benign ancestors through minimal genetic drift.

What may happen next in virus tracking?

Scientists may now use these findings to create a molecular “fingerprint” for high-risk viruses. By mapping protein interactions across different species, researchers could potentially identify which animal viruses possess the traits necessary to infect humans.

According to Krogan, this approach could lead to the development of an early warning system. Such a system may allow the global health community to predict the risk of infection jumps before they occur.

Frequently Asked Questions

What is RaTG13?

RaTG13 is a coronavirus similar to the human coronavirus that only infects bats.

What role does the OrfB9 protein play?

OrfB9 acts as a key factor in determining whether a virus is suppressed by the immune system or can disable immune alarms to replicate in humans.

Which institutions participated in this research?

The study was conducted by researchers from the University of California, San Francisco (UCSF), the Pasteur Institute, and the Fred Hutchinson Cancer Center.

What role should molecular mapping play in the global effort to prevent future pandemics?